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I have 120 year old Victorian home, 4000 square feet 10í ceilings with HW baseboard heat. Iím looking to replace the current boiler (CI 100Kbtu net) with a something new. Iím having a hard time keeping a 66 degree set point when the weather outside goes down to 5 or below, which happens here in upstate New York all too often. My gas bill was over $500 last month and I need to do something to reduce this. I have replaced nearly all of the windows with insulated vinyl and I've caulked and stuffed and caulked as many cracks and holes as I can.

My first step is to pipe a pry-sec loop system with OA reset and put a circulator pump on each of the 4 zones.

My next step is the boiler; I really like the weil-mclain ultra 230 but most professionals I talk to are telling me not to get it. I have read through a lot of threads on this site as well as others and have found mixed opinions on these boilers. It seems most people donít like them due to cost. Others seem to think that they are not as efficient as advertised. I would like to know why people think they canít make their 94% AFUE at temps over 140. All of their literature claims that they are 94% at regular temps and up to 98% at low temps. When you pay $500 a month for gas, every Btu you can get from your boiler counts.

Another suggestion I got was to put in a copper fin laars boiler with a 2 stage gas valve. This solution however will only deliver an 82% AFUE.

Am I wrong in thinking that with an 80% boiler, for every dollar I spend on gas 20cents goes up the flue, & with a 94% boiler only 6 cent goes up the flue?

Any suggestions would be appreciated especially from people that own these units

You have to remember with boilers, AFUE is relative... For an example, when the boiler starts up cold, 94% of each dollar of heat is going into the water, that is then being circulated through home, eventually heating it, however, once the boiler is hot, or once hot water returns to the boiler, less heat can be transfered from the burner to the water, so you start sending more heat up the flue, as well as money, with an 80% boiler, your heating water and not losing efficiency as it runs... I'm sure somebody else here will disagree... Personally I like boilers, but I really don't think the boiler is primary problem... If you do replace your boiler, I'd repipe the whole system... Most likely sediment has built up in the lines, trapping air pockets, and otherwise making your boiler worthless... Of course that is a very expensive plan...

Afue takes into consideration warm up time, and standby loss.
Both an 80, and a 94% boiler are affected by it.

The ultra is modulating, and as the return water temp increases, it will modulate its input lower.
The 230 can go as low as 46,000 btu.

Ultra, Munchin, And Pinnical, are all expensive boilers, but can save you money, with their outdoor reset controls, and burner modulation. Will it save enough to justify the cost? Can't tell from here.

None of them are cure all boilers.

On a zoned system, their main advandage is that they aren't firing at full rate, when a small zone is calling for heat.

BUT, make sure if you get any of them, the company that installs it, knows how to install it properly, and knows how to service them.

I see in all the piping drawings in wm manual as well as most other hi eff boilers that the secondary loop is not closed. Why is that? My idea of a pri-sec loop is to have the boiler inject the water into the loop with tee's less than 12" apart and for each zone to extract the water the same way. All of the manuals seem to show the zone as part of a manifold not giving the water a full loop when the zones are not calling.

One of my issues is recovery time when a zone calls for heat. this is the scenario: when a zone calls, the boiler starts heating the water from whatever the temp is to 180, if a second zone calls, it drops the temp and the boiler keeps running to try and make up the heat, and so on. Meanwhile I'm only running 140 or 150 degree water into my radiation and not getting enough heat to make set pt.

My theory is that these low mas boilers can heat the water faster allowing the radiation to produce more heat. Is this foolish thinking? If the house cools down on a really cold day the boiler can not raise the temp. I usually run a kerosene heater to help it along.

Have you done a heat lose calc on this house? It's big, old, with probabaly little insulation and in a cold climate. 100K doesn't sound like enough. You're system should almost be running constantly since the thermostat doesn't get satisfied. You might need more radiantion in some parts of the house or as you are doing, get better head pressure on the zones and move more water. If you don't go with a modulating burner then a buffer tank would help in preventing short cycling and help balance multiple zones comming on at once.

I havenít done a technical heat loss but I figured 35 Btuís per square foot and 600 Btuís per foot radiation. Using these calcs, there is enough radiation on the site. These are probably the same figures that the original contractor used since it matches exactly. The boiler is probably undersized by about 30kbtu's. Iím certain that the 230K wm ultra would be oversized but with modulation it shouldnít matter since it will throttle down once it makes the return temp set point. It also gives me the extra cushion I need if I add more baseboards. My biggest concern is getting the radiation at 180 or higher as quick as possible and maintaining it through the cycle. The existing boiler is not that old, 4 years. It was a replacement from buderus since the previous one had a cracked heat exchanger and failed before the warranty expired. The entire system is only about 18 years old.

Your baseboard 600 btu rating is 4 gpm, make sure you are actually getting that, before you condemn your curent boiler.
I took it for granite that 100k was the IBR rating of your boiler, not the the input, or DOE.(oops)

Do the load calc, and check each loop length, to make sure you are getting proper flow.

Follow the manufacturers piping diagram and you won't be disappointed.

Thats asking alot,I have never seen any emitter maintain
180 degree its not possible.Unless you dont plan on transfering any btus.How about a zone damper on the baseboard to stop the air current going across the emitter
till the water come up to 180.Just kidding.

I was always taught that you only need a 180 degree water on the coldest day of the year and depending on where you live,may only be a couple weeks out of the year.

Your problem could be where your btus get off at first.
Or as you mention under size boiler,which again to me is not a bad thing unless you are at the coldest day of the year all winter.

Does anyone have any comments on the Pri-sec loop piping outlined in the boiler manuals? As I mentioned before, I would prefer to have the Pri loop closed and always moving flow. All of the low mass boiler diagrams show a manifold configuration.

My thinking is that you tee off the primary loop with the tee's less than 12" apart and run the pri loop gpm at say 20 then you pump off the pri loop into each zone at 10 gpm so your theoretically only taking half of the water wich should keep the return water drop to a minimum. If that description makes any sense.